Re: Setting routes w/ set next hop verify-availability in IOS 12.2


"ttripp" <ttripp@xxxxxxxx> wrote in message
news:19ad57e0-513b-47ac-9f23-9945270c5152@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
I'm trying to set up a 6509 switch with a MSFC2 card to route based on
the reachability of one of two outbound routers. I've set up this
sort of thing using:

ip sla monitor 1
type echo protocol ipicmpEcho 10.100.20.5
frequency 15

ip sla schedule 1 start-time now life forever

track 1 rtr 1 reachability

ip route x.x.x.x 255.255.255.255 10.100.20.5 track 1

on routers that have IOS 12.3 or later. What I'm doing is monitoring
10.100.20.5 with pings, and if the pings work, I'm adding a static
route for a particular host pointing to 10.100.20.5. If the ping
fails, then the static route is remove and the host uses whatever
entry is in the routing table. I've used this approach before
successfully.

Unfortunately, the version of IOS available for the MSFC2 tops out at
12.2, so I can't use this particular solution.

I've come across an older tracking method that is compatible with
12.2, but I'm not sure about its behavior. This is what I've found:

track 123 rtr 1 reachability

interface vlan0
ip address 10.100.30.1 255.255.255.0
ip policy route-map alpha

route-map alpha permit 10
match ip address "ACL-Including-x,x,x,x"
set ip next-hop verify-availability 10.100.20.5 10 track 123

rtr 1
type echo protocol ipIcmpEcho 10.100.20.5
rtr schedule 1 life forever start-time now

I think that will do what I want, setting the next hop for that
particular host if there is a good ping to that specific outbound
router. What I'm not clear on is, what happens if the ping fails?
Will the host then just use whatever route is in the MSFC2's routing
table, or will it not have any route at all and the packets from the
host just drop?

Thanks in advance.

The route map will override the normal routing for that subnet. If the sla
monitor says that the router is available then it set the next-hop to
10.100.20.5, otherwise it will send it to where the routing table says it
should go. I'm curious as to what you are trying to accomplish. Why aren't
you running a routing protocol on 10.100.20.5 or just using a static or
floating-static route?



.

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